Faking injuries on the pitch could jeopardise treatment for players who suffer cardiac arrest and other life-threatening conditions, World Cup final referee Howard Webb has told a FIFA medical conference.

Webb's quick reaction when Fabrice Muamba collapsed on the field in March helped the Bolton midfielder get treatment which saved his life.

Referees' responses could be affected if players "cry wolf" too often, says Webb, who added that Muamba's recovery after his heart stopped beating on its own for 78 minutes is "an unbelievable miracle".

Players who are not seriously injured sometimes seek a tactical edge by staying down longer than necessary to slow the game.

FIFA invited Webb to address a two-day gathering of medical professionals, who have received a comprehensive study of cardiac cases involving football players from football's governing body.

"I would ask everybody in football to think about these situations and ask players not to take advantage," the English referee said on Thursday.

Webb said referees are under pressure when deciding on stopping the game and have a fallen player receive treatment. He warned players against faking pain for fear of affecting referees' judgment.

"If players, and if people, cry wolf too many times, then there is a possibility that maybe we will not react in the way we need to," Webb said.

"If we come under criticism for stopping the games too many times for doctors or physiotherapists to enter the field of play, then referees might be inclined not to stop the game."

Webb said his first priority is players' welfare and he felt a "numb sensation" after Muamba collapsed during an English FA Cup match at Tottenham.

"Without life, there is no football at all. The realisation is, when the CPR starts, is just how serious it is," he said.

"This story has a happy ending thanks to the expertise of the medical staff."

The crowd at White Hart Lane was "urging the doctors to get (Muamba) going again," Webb said, and added: "It was just the most unbelievable crowd reaction I have ever experienced in football and thinking about it now is making me feel emotional."

Muamba was discharged from a London hospital on April 16, but cardiologists have not decided when he can resume playing.